The Python List is one of the most useful sequence in real-time. A list is a sequence of multiple values in an ordered sequence. Unlike Strings, Python List allow us to store different types of data such as integer, float, string etc.
Declare Python Lists
The following are examples of declaring a Python list of different data types.
There are several ways to create a List in Python. The most simplest way is to place the required elects within a square bracket [ ]
A list that contains no values or elements is called as an empty list. By placing an empty square bracket will create an empty list
List_Name = []
The first statement is an integer list of five integer values. The second statement is a string list that contains three string values or three words.
Integer_List = [1, 2, 3, 4, 5] String_List = ['apple', 'Orange', 'Grape', 'Mango']
Python lists allows you to place different data types in a single list. The following one is an example of mixed list, which contains one integer, float and two integer values.
Mixed_List = ['apple', 2, 3.50, 'Mango']
How to access Python List items?
Lists store data in a sequential manner (ordered list). So we can access the list elements with the help of indexes. Moreover, using indexes, we can access or alter/change each and every individual item present in the Lists separately. The syntax to access List items is
List_Name([Index_Number])
Index value starts at 0 and end at n-1 where n is the list size. For example, if a list stores 5 elements then index starts at 0 and ends with 4. To access or alter 1st value use list_name[0] and to access or alter 5th value then use list_name[4]. Lets see the example for better understanding:
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
# Positive Indexing
print(x[0])
print(x[4])
print(x[8])
print('=======\n')
# Negative Indexing
print(x[-2])
print(x[-4])
print(x[-8])TIP: If you are using the Negative values as index then, Python will start looking for items from right to left
OUTPUT
Please use Negative numbers as index to access list items from right to left. I mean, access list items in reverse order.
# How to Access List Items
x = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']
# List Items using Positive Index
print("List Item at Index Position 0 = ", x[0])
print("List Item at Index Position 2 = ", x[2])
print("List Item at Index Position 4 = ", x[4])
print("List Item at Index Position 3 = ", x[3])
print('=======\n')
# List Items using Negative Index
print("List Item at Index Position -1 = ", x[-1])
print("List Item at Index Position -3 = ", x[-3])
print("List Item at Index Position -5 = ", x[-5])
print("List Item at Index Position -6 = ", x[-6])OUTPUT
Alter Python List Items
Since Lists are mutable, apart from accessing items, you can use this index positions to alter or replace the list items.
Iterate Python List items
A For Loop is the most common way to traverse the items in a list. the following statements will help us to iterate the list and print the items inside the list.
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
for Fruit in Fruits:
print(Fruit)Above specified code will work fine to print items inside the list but, In order to alter the individual item we need the index position. To resolve this, we have to use the range function along with for loop as shown below
# Altering List using range
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
for Number in range(len(x)):
x[Number] = x[Number] * 10
print(x)Above specified code will multiply each and every item with 10. If you want to perform the calculation based on condition then, you can use Python If Statement inside the for loop
OUTPUT
In this example, we declared a string list.
- First for loop used the for loop to iterate and prints the list items.
- second for loop used the for loop along with range to iterate each and every list item using position of an index.
Let me show you another example
# Iterate List Items
Fruits = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']
# Iterate List Items
for fruit in Fruits:
print(fruit)
# Iterate List Items using Index
for i in range(len(Fruits)):
print("List Item at Index Position", i, " = ", Fruits[i])OUTPUT
Insert items into List
The following are the list of available options to insert new items into the existing list in Python
- Append(x): This method will help us to add item x at the end of the list.
- Insert(i, x): This method will help us to insert the specified item x at index position i
- Extend(New_List): This method will help us to add all the items in New_List at the end of the list
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
# Adding items using Python append
Fruits.append('Blackberry')
print(Fruits)
# inserting items using Python insert
Fruits.insert(2, 'Kiwi')
print(Fruits)
# Extending List using Python extend
Fruit_new = ['berry','Cherry']
Fruits.extend(Fruit_new)
print(Fruits)OUTPUT
Python List Slicing
In python Slice, the first integer value is the index position where the slicing will start and the second integer value is the index position where the slicing will end.
TIP: List Slicing in Python will go up to second integer value but will not include the value at this index position. For instance, if we specify list[1:4] then slicing will start at index position 1 and ends at index position 3 (not 4).
# List slicing
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
# Slicing List using two indexes
a = x[2:6]
print("Both Indexes = ", a)
# Slicing List using First indexes
b = x[:6]
print("No First Index = ", b)
# Slicing List using Second indexes
c = x[2:]
print("No Second Index = ", c)
# Slicing List without using two indexes
d = x[:]
print("No Indexes = ", d)OUTPUT
Let me use Negative numbers as the index values to slice the list items.
# List slicing
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
# Slicing List using Negative indexes
e = x[-3:]
print("Negative First Index = ", e)
# Slicing List using Negative indexes
f = x[:-2]
print("Negative Second Index = ", f)
# Slicing List using Negative indexes
g = x[-7:-2]
print("Negative First and Second Index = ", g)
# Assigning new values to a List
x[1:3] = ['t','g']
print("After altering = ", x)OUTPUT
From the above screenshot you can observe that,
- If you omit the first index then, Python List Slicing will start from the beginning
- when you omit the second index then, Slicing will start from the first index and continue to the last
- If you are using the Negative values as index then, Slicing starts from right to left
Remove Python List items
There are several ways to delete items from a Lists:
List remove method
If we know the List item or the value inside the List then, we can use python remove method to remove the list item.
# Removing Grape Item from Fruit List
Fruit1 = ['Apple', 'Orange', 'Grape', 'Banana']
Fruit1.remove('Grape')
print(Fruit1)
print('========')
# Removing Orange Item from Fruits List
Fruit2 = ['Apple', 'Orange', 'Grape', 'Banana', 'Orange']
Fruit2.remove('Orange')
print(Fruit2)
print('========')
# Removing Non Existing Grape Item from Fruits1 List
Fruit3 = ['Apple', 'Orange', 'Banana']
Fruit3.remove('Grape')
print(Fruit3)OUTPUT
From the above screenshot you can observe that,
- Within the First set of statements, We are removing the Grape item from the Fruit1 and displaying the remaining list.
- In the Second set of statements, We are removing the Orange item from the Fruit2 and displaying the remaining list. If you observe closely, we have two Orange items in this list but remove() method removed only one item. This is because, remove() method will only remove the first instance of the item and ignores the remaining
- Within the Third set of statements, We are removing the non existing item. That’s why it is throwing an error saying x is not in list
Python List del statement
The Delete function will remove the value at specified index and after deleting, remaining values will be moved up to fill the index gap.
If we know the Index value or you want to delete range of items from the given List then, we can use del statement to remove the list item.
# List Delete example
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
del Fruits[1]
print(Fruits)
print('========')
del Fruits[1]
print(Fruits)
print('========')
del Fruits[1]
print(Fruits)
print('========')
del Fruits[1]
print(Fruits)OUTPUT
From the above screenshot you can observe that,
- Within the First set, We are deleting the item at index position 1, which is Orange and display the remaining list. If you observe closely, after deleting the Orange, the index position of Grape become 1 and Banana as 2
- In the Second set, We are deleting the item at index position 1, which is Grape and displays remaining list.
- Within the Fourth set of statements, We are removing the non existing item. That’s why it is throwing an error saying index out of range
Removing Python List items using pop() method
The pop() method will remove the items at specified index and display the removed element. After removing, remaining values will be moved up to fill the index gap.
If we know the Index value and want to see the deleted value then, we can use python pop() to remove the list item.
# List Pop Method example
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')
Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')
Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')OUTPUT
Python List Methods
The following are the list of methods that are available to perform operations on python list:
Python list copy
List Copy() method help us to shallow copy the list items into completely new list
# Python List copy
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Copying the List using Python Copy() Method
New_Fruits = Fruits.copy()
print("\nNew List : ", New_Fruits)
new_numbers = numbers.copy()
print("New Number List : ", new_numbers)OUTPUT
Python list clear
List clear() method help you to clear all the existing list items. After executing this method, it returns empty list.
# Python List clear
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Clear the List using Python Clear() Method
New_Fruits = Fruits.clear()
print("\nNew List : ", New_Fruits)
new_numbers = numbers.clear()
print("New Number List : ", new_numbers)OUTPUT
Python list sort
List sort() method help you to sort the list items in Ascending order
# Python List sort
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Sort the List using Python sort() Method
Fruits.sort()
print("\nSorted List : ", Fruits)
numbers.sort()
print("New Sorted Number List : ", numbers)OUTPUT
Python list reverse
List reverse() method help you to reverse the items in a list
# Python List reverse
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Reverse the List using Python reverse() Method
Fruits.reverse()
print("\nReverse List : ", Fruits)
numbers.reverse()
print("New Reverse Number List : ", numbers)OUTPUT
list index
Python List index(x) function help you to return the index position of a user specified value in a list
# Python List index
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Index of List items using Python index() Method
print('The Index position of Kiwi = ', Fruits.index('Kiwi'))
print('The Index position of Orange = ', Fruits.index('Orange'))
print('The Index position of Grape = ', Fruits.index('Grape'))
print('The Index position of 0 = ', numbers.index(0))
print('The Index position of 2 = ', numbers.index(2))
print('The Index position of -1 = ', numbers.index(-1))OUTPUT
Python list count
List count(x) function help you to count the total number of times a specified value is repeated inside the list
# Python List count
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Apple', 'Kiwi']
numbers = [9, 4, -5, 0, 9, -1, 4, 9]
print("Original List : ", Fruits)
#Count of List items using Python count() Method
print('Number of Times Kiwi is repeated = ', Fruits.count('Kiwi'))
print('Number of Times Apple is repeated = ', Fruits.count('Apple'))
print('Number of Times Banana is repeated ', Fruits.count('Banana'))
print("\nOriginal number List : ", numbers)
print('Number of Times 9 is repeated = ', numbers.count(9))
print('Number of Times 4 is repeated = ', numbers.count(4))
print('Number of Times 0 is repeated = ', numbers.count(0))OUTPUT
In the below Python Lists program, we are applying all the list methods. This might help you to save the image to see all the functions.
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
x = [9, 4, -5, 0, 22, -1, 2, 14]
#Copying the List using Python Copy() Method
New_Fruits = Fruits.copy()
print(New_Fruits)
#Removing all the List items using Python Clear() Method
New_Fruits.clear()
print(New_Fruits)
# Sorting the List using Python Sort() Method
Fruits.sort()
x.sort()
print(Fruits)
print(x)
# Reverse the List using Python reverse() Method
Fruits.reverse()
x.reverse()
print(Fruits)
print(x)
# Index position of an item in the List using Python index() Method
print('The Index position of Banana = ', Fruits.index('Banana'))
print('The Index position of -1 = ', x.index(-1))
# Counting items in the List using Python count() Method
y = [9, 4, 1, 4, 9, -1, 2, 4]
print('Number of Times 4 is repeated = ', y.count(4))
print('Number of Times 9 is repeated = ', y.count(9))OUTPUT
List sum
The List sum function in Python is to find the sum of all items available in a given lists
# Python List sum
int_list = [5, 10, 15, 20, 25]
print("List Items : ", int_list)
# sum of list elements
total = sum(int_list)
print("\nThe sum of total items in this list = ", total)OUTPUT
Python List min
The Python List min function is used to find the minimum value among the given list items.
# Python List min
int_list = [50, 10, 150, 20, 205, 500, 7, 25, 175]
print("List Items : ", int_list)
# Minimum list element
minimum = min(int_list)
print("\nThe Minimum item in this list = ", minimum)OUTPUT
List max
The Python List max function is to used to find the maximum value among the given list items
# Python List max
int_list = [50, 10, 150, 20, 205, 500, 7, 25, 175]
print("List Items : ", int_list)
# Maximum list element
maximum = max(int_list)
print("\nThe Maximum item in this list = ", maximum)OUTPUT
Python List Arithmetic Operations Example
In this example we will show you, How to use Arithmetic Operators on Python Lists to perform arithmetic Operations.
# Python List count
x = [10, 20, 30, 40]
y = [15, 25, 35, 45]
# using + Operator
total = x + y
print("\nAddition : ", total)
# using * Operator
multi = x * 2
print("Multiplication : ", multi)
multi2 = y * 3
print("Multiplication of Y : ", multi2)OUTPUT
From the above screenshot you can observe that,
- + operator is concatenating the python Lists
- * operator is repeating the list for given number of times. Here it is three time.
